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"ii L.. hmfmmw A EMALS FOR WIRELESS if lus-d NGV. 9, WM '4 Sheetsnsbeet l l l K l l l s T. L. EcKERsLEY lERALS FOR WIRELESS SIGNAIING Filed Nov. 1.9. 1921 4 Sheets-Sheet 2 S Snom/woz T. L. ECKERSLEY H' .JTW @51, his www Oct. 9, 1928. "MS,

T. L. ECKERSLEY AERIALS FOR WIRELES S SIGNALI NG Filed Nov. 19. 1921 l sneetswsneet 3 f/g. 5 S

@mi L T. L.. @Mmmm AERIALS FOR WIRELESS SIGNALING Patented that. 9, 1928.

llltll'lll) Silrl'lES THOMAS LYD'WEL'L ECKERSLEY, F Drllil'B'llttY, E555 CORPORATION UF llMERlCri.,

.application filed November 19, 1921, Serial No. attic-tt?, and in Stir.. a

The acrials used in wireless signaling are con'unonly connected to earth though it has before been proposed to connect theIn to a cajxiacity instead ot to earth.

lhe object ot this invention is to provide on improved capacity or screen to which an aerial may be connected, and by which the aerial may be rendered more ellicient than it is connected to earth or to a capacity as previously arranged.

According to this invention l so construct thescreen that the total electrostatic and electroniagnetic action of the aerial and screen together upon the earth is as small as is practically possible. rlhe screen is formed of a number ot equal horizontal wires. each ot which is at least equal in length to the height ot the aerial plus the length of the horizontal part it any ol the aerial.

lhe mean distance between any wire and the neat to it should lie between two and tour times the height at which the wires are arranged above the ground, which height should be as small as is practically possible.

Since the most important dielectric losses in an earthed aerial. are those necessarily inA troduced by the presence of Vegetation at the surface ot the earthg the screen should so Yfar as is possible be arranged above the vegetation.

rlhe screen should be supported on metal poles. and suitably insulated from the poles, wooden poles being unsatisfactory on account ot dielectric losses.

This specification oit the screen dimensions is based on the following considerations:

'.lhe losses in any aerial may be classified under the following); headings (l) Losses due to earth currents caused by the currents in the aerial.

(2) Losses due to the presence oli imperliect dielectrics in the lield of the aerial.

(il) Brush discharge and corona and leal:- age losses. Y

l find that the use ot a screen of wires, as specilied largely reduces the losses under headings (l) and (2).

The horizontal electric forces in the earth which produce the earth currents, and hence the earth losses, are caused by the Varying currents in the horizontal wires of the aerial.

llVhen a screen is used the elliect oi the currents in the aerial wires in producing earth currents is reduced, on account ot the in January a. ies-"31.

ooposition currents in the wires oif the screen. ice the loss due to these earth currents is reduced when a suitably designed used. n wires should be arranged so as to annui as nearly as possible the elliect on the earth olf the aerial currents; for this purpose the wires should be placed so as to cover as unit nly as possible the area underneath the aerial. and should run parallel to the horizontal portions ol' the aerial if any.

l will .now describe in detail the screens to be used with the various Aforms et aerial,

iwings wherein: Fig. l, represents the prmable distribution oit electric torce in a plane perpendicular to the wires ot an aerial; Fig. 2, is the saine when the screen ot iny invention is used; 3 shows the probabl.-. distribution et potential in the case or' lli Fin. Ll is a diagram perpendicular to the aerial wires showing the relative loca tion of the aerial and a inoditied toi-in et' screen; lig. 5 is a. longitudinal diagram oi the arrangement ot Eig". lg Fig. 5 is a plan View oit an optional arrangement ot. the screen shown in 5; Fig. (i shows the .torni of screen tor use with a tan shaped aeria`; 7 shows the means tor balancingn diliierences in electrical lenrgth in the screen wires; Figi. 5l shows means ror halancing; out the elliect oi? iuisyinmetrical induction in 'the aerial with. i fd to the screen; lflig. ll shows the method ot attaching the aerial to s en for a ae ldelerringg' now more par iularly to the drawings For an aerial olf "l" or lM iorin, the screen should be constructed according' to the general rules Eeinen above as regards length and spacing ot the wires; tl se should he parallel to the horizontal wires ot the aerial and the breadth of the screen should be equal to the ln'eadth of the aerial. plus twice its height.

.he addition oi" wires in the sceen beyond a certain number cannot reduce the resistance appreciahly. so that it is not economical to use incre than a specified num.- loer ol'A wires.

rllhis number neen not exfieed the number obtained by dividing' the breadth of the screen by twice the height ot the screen,

; inane to the accompanying,

while the number should not be so sinan that the distance between any Wire and the next is greater than four times the height of the screen.

The probable distribution of electric torce in a plane perpendicular' to the Wires of the aerial and screen is shown in Figures 1 and 2 of the accompanying' drawings. ln Figures l and 2, A, A are the Wires oi the aerial and in -Figure il are the Wires of the screen. v

This distribution is practically the saine as that due to equal and opposite charges on aerial and screen.

The elect-ric torce leaking: throng-h only depends on the ratio of the distance between adjacent screen Wires to the height thereof above the ground.

'lhevertical electric forces at the surface orp the earth are responsible for the losses (2)x above.

lllhen a screen is used the induced charges on it intercept a large proportion ot the vertical force, and these losses' are consequently reduced.

rlhese considerations, which have been conlirmed experimentally7 substantiate the claim that an aerial connected to a screen as specified in the opening paragraph is materially more etlicient than the same aerial connected to earth. As long` as the breadth of the screen and the saine spacing ratio conform with the rules `given above the losses are practically independent ot the height.

The height of the screen is therefore determined almost solely by considerations of cost and practicability.

The cost oit the screen Will be great it it is too high or too low; for the former case involves the use of excessively l igh supports, and the latter the use of an excessive number otV Wires. Hence the screen should be at either the minimum practical. height or at such a height as will reduce the cost of the screen to its minimum. so long as this does not involve a serious reduction of the eliective radiatingheight ot the aerial.

ln'order to prevent the mean potential olf the system consisting` of the screen and aerial diliering largely from that oi' the earth, a point on the loading` coil may be connected to earth. This point should be the node of potential ot the oscillation in the system. 'for when such a nodal point is connected to earth the high frequency oscillations are unaltered and no increase of resistance occurs. The probable distribution ot potential throughout the system is shown in Figure 3 Slight modifications may be made in the height and spacing ratio to suit special con ditions.

(l) lt owing to Want of space the screen cannot be extended beyond the aerial an amount equal to the height of the aerial the outside and end Wires may be raised so as more important part ot llhc screen as shown in Fig. 5u. Y l' "be fl'crccn has to pass over huddings, the sigiacing ratio may be reduced in the ncif'hborhood to suit the cllcctiii'c height the een over the building.

The rules for thc arranfrenicnt oi" the screen to be used with an undnrell-,t or radial type aerial are similar 'to those for "l` or lshaped aerial screen.

The screen should consist ot n. nuuibcr ol" vv" in a horizontal plane and radiating; '.-roin point beneath lhc ccrtrc oil the ae-v rial, and the spread oit the wires .should be sufficiently I eat to cover the whole il the ground beneath the aerial. 'l`l1o length of each Wire should be equal to "i rai/luis olf the aerial plinheight s racing* el? thc Wires should be such that the dimauce betiveen the middle points olf tivo adjacent Wires should be between tiro and tour liinca the height of the screen above the earth the outer portions oil the wires being iicrlrcd il? the larger distance be cinployed ln the case oi a fau shaped acria l in which the angle of the tan is smallv .say han -l degrees it is inadvisablc lo have tlu :fci cu in the form of a lian. lt should be a parallel wire screen ot the same forni as that used with an ordinary type aerial. ilill., natively it should be ot the torni shown iu Figure G, ln this figure thc aerial rires are carried by three masts lll and thc scrccu is termed ot Wires El S radiating); l'l'om a centre the outside wires being` parallel to the outside Wires of the aerial. lhc distance between each outside wire li and thc projection on the plane di? the :icrccu t outside Wire A. should be as `great as the height ot the aerial.

For a vertical. aerial havin;r no horinontal Wires the screen if'hould consist ot wires of equal length radiating; at equal angles Vtroni the aerial a a contre.. the ha th ot cach Wire being` equal to the heil-ht ci the :ir-rial and the cistanee between the u'iiddle point of any Wire and the next e; tivo to :tour times the height ol`V i. u. screci; as: hcl'ore iii the larger ratio be eniplincd the outer portions of the wires should be forked.

rlhe screen Wires may toria :i system poft sessing one more natural periods o o3; 'llations of its oivn, apz'rt troni thc oscillations in the aerial. l' the u'orlrinp; period of the aerial. is at near one oit their periods oscillations may be sci" up in the sct'ccu Which do no use'lul ivorr aud only absorb energy. ln order to eliminatie libel-ii oscillations the potential nodes oli all of them the bei

lill

Ilo

lll?) electrical dii'llerences ot ill) should, if possible, be at the point at which all the screen Wires join, and the aeral should then be attached at this point so that interaction between the aerial system and the system formed by the screen Wires is eliminated.

This can be done :M

(l) By making the length ot the Wires as nearly equal as possible.

By balaiicing up the small. effective length by inserting as shown in Figure 7 suitable inductance coils L in each Wire or group olf Wires ci the screen, which is here shown divided into tour sections or groups.

ln cases Where the aerial wires are placed unsyininetrically with respect to the circuits which are 'loaned by the screen vvires and in which the undesirable oscillation talc ing place, the currents in the aerial inay induce in those circuits lil. M. ls which will produce oscillations even when the aerial attached at the node ln this case the effect of these lil. lvl. ls can be partly annulled by shifting the point of attachment of the ae- 1iai away from the anode. This can be done by a slight adjustment of the inductances referred to above, or by providing a suitable inductive or capacitive coupling between the aerial and the circuit in which the oscilla tions are taking place so as to balance out the effect ci' the unsynnnetrical induction.

` Figure S shows a coil P connected to the aerial and coupled to a coil Q connected to the screen.

The natural period of the screen oscillations may be removed from the Working point (probably below the natural period of the aerial) p by connecting the ends oit the screen together with a Wire, thus avoiding interaction ot the systems This has the adi'fantage that circulating currents may be induced in the closed cir cuits in the screen formed by this Wire; although the resistance may be largely reduced in this Way it is not so edective balancing, though it is simpler.

To eliminate the effect ol the oscillations Which may occur in the circuits formed by the screen Wires the point ci attach nient oi the aerial to the screen may be earthed thereby forcing this point to be a node of potential, but this should only be done when the Wave length employed. is such that there is no danger of the oscillations due to the screen itself acting as a "l aerial interfering With the main oscillations.

lWhen the aerial is oi" "l" form vvith a screen under each arm ot the l the best Way to bal ance out the oscillation :from end to end of the screen is to insert a small inductance between the tvvo halves of the screen and to iind the node and attach the aerial there as shown in Figure 9.

Each halt of the screen should be balttS anced up separately as indicated above. for l" aerials.

This has the advantage that not only is it easy to lind 'the node but oscillations across the screen are eliminated and the natural oscillations of the aerial and favored.

Having described my invention, what l claim is:

lu in aerial system consisting of the tonibination oi? a conductively related aerial, aerial indue-tance, and screen, said screen ing insulated from the earth and composed oi a plurality` ot substantially horizontal Wires each of which is ci a length at least equal to the height of the aerial above the ground plus the length oi the vertical gro-- jection oif the aerial, and each olf' which is "rom the nent adjacent wire bv a scaced :t u mean distance oit between two and tour times the height of said screen above the ground, the outer portions of said screen being raised above the remaining portions.

2. in aerial system consisting of the conibination ot a conductively related aerial, output inductance, and screen, said screen being insulated from the earth and composed of a plurality o1c substantially horizontal Wires each or which is ot a length at least equal to the height ci: the aerial above the ground plus the length of the vertical projection of the aerial, the outer portions oi said screen being raised above the remaining portions.

3. in aerial system consisting of the cornbination ol a conductively related aerial, output inductance, and screen, said screen being insulated Yfrom the earth and composed of a plurality oi substantially horizontal Wires each or which is oi' a length at least equal to the height of the aerial above the ground plus the length of the vertical projection ot the aerial, the outer portionsof said Wires being forked substantially as described, and the outer portions of said screen being raised above the remaining portions.

il. The combination With an aerial of a screen and a plurality of inductances, said screen being suspended above the earth and insulated therefrom and composed of a plurality of Wires which are horizontal throughout the greater portion thereof, and ot a length at least as great as the vertical projection oi said aerial plus the mean height oit said aerial above the ground, and spaced a distance between tivo and four times their height from the earth, said screen being of a Width at least as great as the Width ot the projection oi said aerial upon the earth plus the height of said aerial above the ground, and said inductances being arranged to coinpensate l'or the differences in electrical length oithe various Wires composing said screen.

5. The combination With an aerial of a soreen :tor aidingl the radiation of electromagnetic Waves and consisting of a plurality of horizontal Wires each of which is of a length at least equal to the height of the aerial above the ground plus the length of the vertical projection of the aerial, and induotanees inserted in the screen for ooinpensating for the differences in electrical length of said Wires, said screen being concluetively connected to said aerial at the potential node point or' said screen. Y

6. An aerial system consisting of the eoinbination or a. eonductively related aerial, output induetance, screen, and ground connection, said screen being insulated from the earth and Composed of a plurality of substantially horizontal Wires, each oi which is oli' a length at least equal to the height of the aerial above the ground plus the length of' the vertical projection of the aerial, and said ground connection being inade at the potential node oil said output induetanee.

7.4 Ain aerial system consisting of the co1nbination of a conduetively related aerial, ou l'- put induetanee, screen, and ground connection, said Screen being insulated from the earth and composed of a plurality of sulstantially horizontal Wires, each of which is of a length at least equal to the height of the aerial above the ground plus the .length oiC the vertical projection of the aerial, the outer portions of said screen heilig raised above the remaining portions, and said ground connection being made at the potential node of said output induotanoe.

THOMAS LYDlVELL ECKERSLEY.

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